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Influence of optional biometric variables on refractive outcomes predicted through the Kane and Barrett UII formulas

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First Author: M.Raimundo PORTUGAL

Co Author(s):    E. Neves   J. Simão   C. Lobo   J. Murta           

Abstract Details

Purpose:

Modern intraocular lens (IOL) calculation formulas depend on a set of mandatory biometric parameters – axial length, keratometry, anterior chamber depth – as well as optional biometric parameters. This can be seen in the Barrett Universal II and the Kane formula which contain optional parameters such as lens thickness (LT) and white-to-white distance (WTW) or LT and central corneal thickness (CCT), respectively. Such parameters may not be measurable using older optical biometry devices. Currently there is a lack of evidence regarding their effect on refractive outcomes. We compare outcomes of cataract surgery with and without the use of optional parameters.

Setting:

Tertiary university hospital.

Methods:

Retrospective consecutive case study of eyes that underwent uncomplicated cataract surgery with trifocal intraocular lens implantation (Alcon PanOptix®). We compared the predicted spherical equivalent (SE) for the implanted lens as obtained through the Kane and Barrett Universal II (UII) formulas to the postoperative SE obtained by subjective refraction 6-12 post-operatively. To assess the influence of optional variables for the Barrett UII and the Kane formulas back-calculation without those parameters was performed. Primary outcomes included mean arithmetic error (ME), standard error (SD), mean absolute error (MAE) and median absolute errors (MedAE).

Results:

Seventy-nine eyes were included (n=79). After optimization, the MAE obtained through the Kane and Barrett UII formulas without optional parameters was 0.207 and 0.213, respectively (p>0.05). MedAE was 0.171, 0.173, respectively (p>0.05). With the inclusion of both optional parameters for the Barrett UII and Kane formulas, the post-operative SE prediction changed by more than 0.1D (absolute values) in only 15.2% (n=12) and 17.7% (n=14) of eyes, respectively. In this subset, a more accurate prediction was seen in 50% of cases (n=6 and n=7), with a worse prediction in the other 50% (n=6 and n=7).

Conclusions:

In our sample, the inclusion of optional biometric variables in the Barrett UII and Kane formulas did not provide any significant refractive benefit.

Financial Disclosure:

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